In order to provide realistic video services, a multiview video has been used in various application fields. Such a multiview video is compressed, and the compressed multiview video is transmitted to a user for providing related service. Although the multiview video is compressed according to a conventional coding and compressing scheme, it requires a large quantity of data as large as two times of the number viewpoints to be transmitted to a user. Accordingly, a wide bandwidth is required to provide a related service for the multiview video.
In order to effectively transmit the multiview video data, a compression rate is improved using the redundant information of an adjacent camera viewpoint and a current viewpoint. The compression rate is generally improved by removing the redundant information from a set of data having high correlation, transforming it to data without correlation and coding the transformed data. Conventional AVC based multiview coding uses only a temporal reference picture buffer in predictive coding between viewpoints. That is, the conventional AVC based multiview coding restrictively consider the efficiency of the predictive coding between viewpoints. Therefore, it requires the efficiency of the predictive coding to be improved.
As conventional technologies for encoding a plurality of pictures, a method for processing a stereoscopic video regarding to two viewpoints was introduced. Also, as a method for processing multiview video based on more than three viewpoints, a method of processing a multiview video regarding to a multiple lens reflex solid, and a method of processing a multiview video obtained from cameras arranged adjacently were introduced. A technology for encoding using a MPEG-2 multiview profile (MVP) and a MPEG-4 temporal scalability (TS) was widely used to encode stereoscopic video.
A technology of encoding using the MPEG-2 MVP and the MPEG-4 TS was introduced in Korea Patent Application No. 10-2002-0021757, and Korea Patent Application No. 10-2003-0002116. Also, such a technology was introduced in an article by Kwang-Hoon Son, entitled “multiview video CODEC using view scalability”, and another article by Yong-Tae Kim, entitled “method for estimating motion and variation in stereoscopic video with boundary directivity”.
In Korea Patent Application No. 10-2002-0021757 and the article of Son, a group of picture (GOP) was commonly proposed. Also, the Korea Patent Application No. 10-2002-0021757 uses a MPEG-2 based CODEC. The Korea Patent Application No. 10-2002-0021757 focus on compression, and the article of Kim focus on adding scalability in a unit of view using a MPEG-2 based CODEC.
The Korea Patent Application No. 10-2003-0002116 creates a bit stream of a central viewpoint, and the created reference picture of the central viewpoint is used to create a bit stream of left/right viewpoint picture. In Kim's article, a method of increasing a compression rate by minimizing the error of predicting spatial and temporal disparity in a stereo video.
Excepting Korea Patent Application 10-2003-0002116, the above described conventional technologies use single predicted motion vector when a P-picture is encoded because of the comparability with MPEG-2. Since two vectors are used for encoding a B-picture, a motion vector from a previous frame and a disparity vector from an adjacent viewpoint in a current time are used. Korea Patent Application 10-2003-002116 uses one motion vector and one disparity vector to refer the central viewpoint picture. In case of B-picture, vectors are used as like typical MPEG-2, and no B-picture is present on a time axis in a left/right viewpoint.
These conventional technologies do not use more that two motion vectors or disparity vectors due to the comparability with MPEG-2. When the B-picture of MPEG-2 is encoded, bi-directional predictive coding on time axis cannot be performed. Furthermore, the distance between viewpoints, and the size of a base line is regarded by extending the number of viewpoints when the I-picture is encoded. It is not proper disparity vector prediction method. It requires a step for transforming an adjacent viewpoint to a current viewpoint.
Also, the compression rate is decreased because the disparity vector and the motion vector are encoded with a same scheme although they fundamentally are different. That is, the size of the disparity vector is generally larger than the motion vector. When a motion vector is selected at a previous block and a disparity vector is selected at a following block, the difference of vectors is not effective in a view of characteristic of encoder that performs entropy-coding on the vector difference. Furthermore, a context reflected affection cannot be obtained when performing the context adaptive entropy-coding as like AVC.